Banded Agate (Orca Agate)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Grey, blue, white, and black banding; Luster: Waxy to vitreous; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.6-2.64

Formation & Geological History

Formed as a result of silica-rich groundwater filling cavities (vugs) in volcanic or sedimentary rocks over thousands of years; predominantly found in Madagascar for this specific color pattern.

Uses & Applications

Primarily used for ornamental purposes, lapidary art, jewelry, and as a collector's specimen for spiritual/metaphysical practices.

Geological Facts

This specific variety is nicknamed 'Orca Agate' due to its resemblance to the skin patterns of a Killer Whale. Agates often form in concentric layers that record the chemistry of the water as it percolates through rock.

Field Identification & Locations

Identify by its characteristic banding, waxy feel when polished, and transclucency when held to light. It is commonly found in basaltic geodes in Madagascar.

Identified on: 4/16/2026

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